Pump apparatus

ABSTRACT

A pump apparatus includes: a spool valve including a first land portion, a second land portion, and a third land portion; a first pressure chamber into which an upstream pressure of the metering orifice is introduce; a second pressure chamber into which a downstream pressure of the metering orifice is introduced; a third pressure chamber into which the pressure of the discharge passage is introduced; a fourth pressure chamber into which a low pressure is introduced; and a first fluid pressure chamber side communication passage which is formed in the pump housing which is arranged to selectively supply the pressure of the third pressure chamber and the pressure of the fourth pressure chamber to the first fluid pressure chamber in accordance with the movement of the spool valve.

BACKGROUND OF THE INVENTION

This invention relates to a pump apparatus which is used as a driving source of a continuously variable transmission, a power steering apparatus and so on.

A Japanese Patent Application Publication No. 2012-87777 discloses a pump apparatus including a pump housing including a pump element receiving portion; a pump element which is driven to be rotated, and which is to arranged to suck and discharge a hydraulic fluid; a discharge passage arranged to introduce the hydraulic fluid discharged by the pump element to a supplied portion; a metering orifice provided in the middle of the discharge passage; and a flow rate control valve arranged to control is the discharge amount of the hydraulic fluid by the pump element.

The pump element includes a rotor arranged to be rotated as a unit with the drive shaft; a plurality of vanes which are provided to an outer circumference portion of the rotor to be moved in a radially outward direction and in a radially inward direction; and a cam ring which is provided radially outside the rotor, and which is arranged to be moved in a direction in which an eccentric amount of the cam ring with respect to the rotor is increased and decreased. Moreover, the pump element is set so that a pump discharge amount becomes larger as the eccentric amount of the cam ring is increased.

The flow rate control valve includes a cylindrical valve receiving hole; a spool valve which is slidably received within the valve receiving hole; and a first pressure chamber which is formed in the control valve receiving hole on one end side of the spool valve, and into which an upstream pressure of the metering orifice is introduced; and a second pressure chamber which is formed in the control valve receiving hole on the other end side of the spool valve, and into which the downstream pressure of the metering orifice is introduced.

Moreover, the flow rate control valve includes a communication passage arranged to introduce the hydraulic oil used for the eccentric amount control of the cam ring. The flow rate control valve is arranged to draw a part of the hydraulic oil within the first pressure chamber or the second pressure chamber in accordance with the disposition of the spool valve which is moved in the axial direction based on the pressure difference between the first and second pressure chambers, and to use this part of the hydraulic oil for the eccentric amount control of the cam ring so as to control the pump discharge amount.

SUMMARY OF THE INVENTION

However, in the conventional pump apparatus, a part of the hydraulic fluid within the first pressure chamber or the second pressure chamber is used for the eccentric amount control of the cam ring. Accordingly, the variation of the pressure within the first pressure chamber or the second pressure chamber is frequently generated. The position control of the spool valve becomes unstable in accordance with the variation of the pressure within the first pressure chamber or the second pressure chamber. Consequently, the eccentric amount of the cam ring which is controlled based on the disposition of the spool valve becomes unstable, so that there is generated the variation of the pump discharge amount.

It is, therefore, an object of the present invention to provide a pump apparatus devised to solve the above mentioned problem, to improve accuracy of position control of a spool valve, and thereby to stabilize the pump discharge amount.

According to one aspect of the present invention, a pump apparatus comprises: a pump housing including a pump element receiving portion which is formed within the pump housing; a drive shaft which is inserted within the pump element receiving portion, and which is rotatably supported by the pump housing; a rotor which is provided within the pump element receiving portion, which is driven by the drive shaft to rotate, and which includes a plurality of slots in a circumferential direction; a plurality of vanes which are provided in the slots of the rotor to be moved in a radially outward direction and in a radially inward direction; a cam ring which is arranged to be moved within the pump element receiving portion, which has an annular shape, and which forms a plurality of pump chambers radially inside the cam ring, with the rotor and the vanes; a suction opening which is formed in the pump housing, and which is opened in a suction region in which volumes of the plurality of the pump chambers are increased in accordance with the rotation of the rotor; a discharge opening which is formed in the pump housing, and which is opened in a discharge region in which the volumes of the pump chambers are decreased in accordance with the rotation of the rotor; a discharge passage connected with the discharge opening; a metering orifice which is formed in the middle of the discharge passage; a first fluid pressure chamber which is formed between the pump element receiving portion and the cam ring, and which is formed on a side on which a volume of the first fluid pressure chamber is decreased when the cam ring is moved on the side on which the eccentric amount of the cam ring with respect to the drive shaft is increased; a second fluid pressure chamber which is formed between the pump element receiving portion and the cam ring, and which is formed on a side on which a volume of the second fluid pressure chamber is decreased when the cam ring is moved on the side on which the eccentric amount of the cam ring with respect to the drive shaft is increased; a control valve receiving hole which is formed in the pump housing; a spool valve which is arranged to be moved within the control valve receiving hole, the spool valve including; a first land portion which is provided on a first end side of the spool valve in a movement direction of the spool valve, a second land portion which is provided on second end side of the spool valve in the movement direction of the spool valve, and a third land portion which is provided between the first land portion and the second land portion in the movement direction of the spool valve; a first pressure chamber which is formed within the control valve receiving hole, which is provided on the first end side of the first land portion in the movement direction of the spool valve, and into which an upstream pressure of the metering orifice is introduced; a second pressure chamber which is formed within the control valve receiving hole, which is formed on second end side of the second land portion in the movement direction of the spool valve, and into which a downstream pressure of the metering orifice is introduced; a third pressure chamber which is formed within the control valve receiving hole, which is provided between the first land portion and the third land portion in the movement direction of the spool valve, and into which the pressure of the discharge passage is introduced; a fourth pressure chamber which is formed within the control valve receiving hole, which is provided between the second land portion and the third land portion in the movement direction of the spool valve, and into which a low pressure is introduced; and a first fluid pressure chamber side communication passage which is formed in the pump housing, which includes a first end portion which is connected to the valve receiving hole, and a second end portion which is connected to the first fluid pressure chamber, and which is arranged to selectively supply the pressure of the third pressure chamber and the pressure of the fourth pressure chamber to the first fluid pressure chamber in accordance with the movement of the spool valve.

According to another aspect of the invention, a pump apparatus comprises: a pump housing including a pump element receiving portion which is formed within the pump housing; a drive shaft which is inserted within the pump element receiving portion, and which is rotatably supported by the pump housing; a rotor which is provided within the pump element receiving portion, which is driven by the drive shaft to rotate, and which includes a plurality of slots in a circumferential direction; a plurality of vanes which are provided in the slots of the rotor to be moved in a radially outward direction and in a radially inward direction; a cam ring which is provided within the pump element receiving portion, which has an annular shape, and which forms a plurality of pump chambers radially inside the cam ring, with the rotor and the vanes; a suction opening which is formed in the pump housing, and which is opened in a suction region in which volumes of the plurality of the pump chambers are increased in accordance with the rotation of the rotor; a discharge opening which is formed in the pump housing, and which is opened in a discharge region in which the volumes of the pump chambers are decreased in accordance with the rotation of the rotor; a discharge passage connected with the discharge opening; a metering orifice which is formed in the middle of the discharge passage; a control valve receiving hole which is formed in the pump housing; a spool valve which is arranged to be moved within the control valve receiving hole, the spool valve including; a first land portion which is provided on a first end side of the spool valve in a movement direction of the spool valve, a second land portion which is provided on second end side of the spool valve in the movement direction of the spool valve, and a third land portion which is provided between the first land portion and the second land portion in the movement direction of the spool valve; a first pressure chamber which is formed within the control valve receiving hole, which is provided on the first end side of the first land portion in the movement direction of the spool valve, and into which an upstream pressure of the metering orifice is introduced; a second pressure chamber which is formed within the control valve receiving hole, which is formed on second end side of the second land portion in the movement direction of the spool valve, and into which a downstream pressure of the metering orifice is introduced; a third pressure chamber which is formed within the control valve receiving hole, which is provided between the first land portion and the third land portion in the movement direction of the spool valve, and into which the pressure of the discharge passage is introduced; a fourth pressure chamber which is formed within the control valve receiving hole, which is provided between the second land portion and the third land portion in the movement direction of the spool valve, and into which a low pressure is introduced; and an outlet passage which is provided in the pump housing, which includes a first end portion connected to the valve receiving hole, and a second end portion connected to the suction opening, and which is arranged to discharge the hydraulic fluid within the third pressure chamber to the suction opening's side in accordance with the movement of the spool valve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral sectional view showing a pump apparatus according to embodiments of the present invention.

FIG. 2 is a sectional view taken along a section line A-A of FIG. 1.

FIG. 3 is a schematic view which shows a connection relationship between a flow rate control valve and a discharge passage in the pump apparatus according to a first embodiment of the present invention, and which shows a case where a pressure difference on forward and rearward sides of a metering orifice is small.

FIG. 4 is a schematic view which shows a connection relationship between a flow rate control valve and a discharge passage in the pump apparatus according to the present invention, and which shows a case where the pressure difference on the forward and rearward sides of the metering orifice is small.

FIG. 5 is a schematic view showing a connection state between a flow control valve and a discharge passage in a pump apparatus according to a second embodiment of the present invention.

FIG. 6 is a schematic view showing a connection state between a flow control valve and a discharge passage in a pump apparatus according to a third embodiment of the present invention.

FIG. 7 is a schematic view showing a connection state between a flow control valve and a discharge passage in a pump apparatus according to a fourth embodiment of the present invention.

FIG. 8 is a schematic view showing a connection state between a flow control valve and a discharge passage in a pump apparatus according to a fifth embodiment of the present invention.

FIG. 9 is a schematic view showing a connection state between a flow control valve and a discharge passage in a pump apparatus according to a sixth embodiment of the present invention.

FIG. 10 is a schematic view showing a connection state between a flow control valve and a discharge passage in a pump apparatus according to a seventh embodiment of the present invention.

FIG. 11 is a schematic view showing a connection state between a flow control valve and a discharge passage in a pump apparatus according to an eighth embodiment of the present invention.

FIG. 12 is a lateral sectional view showing a pump apparatus according to a ninth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of pump apparatuses according to the present invention are explained in detail with reference to the drawings. Besides, the below-described embodiments show the pump apparatuses mounted to a continuously-variable transmission (CVT) of a vehicle.

First Embodiment

This embodiment shows the pump apparatus according to the present invention which is applied to a variable displacement vane pump 1.

As shown in FIG. 1 to FIG. 4, this variable displacement vane pump 1 includes a pump housing 2 including a pump element receiving chamber 2 a which is formed within the pump housing 2, and which is a pump element receiving portion that has a cylindrical shape; and a pump element 3 received in the pump element receiving chamber 2 a. The variable displacement vane pump 1 performs a pump operation by rotatably driving the pump element 3 by a drive shaft 4 inserted through the pump element receiving chamber 2 a.

As shown in FIG. 2, the pump housing 2 includes a housing main body 5 which has a bottomed cylindrical shape; and a housing cover 6 which closes an opening portion of the housing main body 5. The housing main body 5 and the housing cover 6 are tightened and fixed together by a plurality of bolts 7.

As shown in FIG. 1 and FIG. 2, the pump element 3 includes an adapter ring 8 which has a substantially annular shape, and which is mounted and fixed in an inner circumference of a cylindrical portion 5 a of the housing main body 4 that is a circumferential wall of the pump element receiving chamber 2 a; a cam ring 9 which has a substantially annular shape, and which is arranged to be moved within an inside space of the adapter ring 8 that has a substantially elliptical shape; a rotor 10 which is disposed radially inside the cam ring 9, and which is arranged to rotate as a unit with the drive shaft 4; and a pressure plate 11 which is a substantially disc shape, which is disposed on a bottom wall portion 5 b of the housing main body 5, and which sandwiches the cam ring 9 and the rotor 10 with the housing cover 6.

As shown in FIG. 1, the cam ring 9 is arranged to be rolled on a rolling support surface 8 a formed on an upper portion of the inner circumference of the adapter ring 8. The cam ring 9 is pressed against the rolling support surface 8 a by the discharge pressure acted to the inside of the cam ring 9. Moreover, the adapter ring 8 is provided with a seal member 13 disposed in a seal groove which has an arc shape, and which is formed by cutting in the adapter ring 8 at a position to confront the rolling support surface 8 a in the radial direction. These rolling support surface 8 a and the seal member 13 are pressed and abutted on the outer circumference surface of the cam ring 9. With this, there are separated a first fluid pressure chamber 14 and a second fluid pressure chamber 15 which are located between the adapter ring 8 and the cam ring 9.

Moreover, the adapter ring 8 includes an arc groove which is formed, by cutting, on an upper portion of the inner circumference surface of the adapter ring 8, at a position adjacent to the rolling support surface 8 a. A pin 12 arranged to restrict rotation of the cam ring 9 is received and held in the arc groove of the adapter ring 8. With this, the relative rotation of the cam ring 9 within the adapter ring 8 is restricted. Moreover, the cam ring 9 is arranged to be constantly urged in a direction in which an eccentric amount of the cam ring 9 with respect to the rotor 10 becomes maximum, by a spring force of a return sprig 16 which is elastically abutted on the outer circumference surface of the cam ring 9 on the second fluid pressure chamber 15's side.

The rotor 10 is integrally connected with the drive shaft 4 by a spline joint. When the drive shaft 4 is driven by an engine (not shown) to be rotated, the rotor 10 is rotated in a clockwise direction (a direction shown by an arrow) of FIG. 1 in accordance with the rotation of the drive shaft 4. Moreover, the rotor 10 includes a plurality of slots 17 formed on an outer circumference portion of the rotor 10, which extend in radial directions, and which are formed by cutting at a substantially regular interval in the circumferential direction. A plate-shaped vane 18 is received within each of the slots 17 to be moved in the outward direction and the inward direction of the rotor 10.

The vanes 18 are arranged to be urged toward the inner circumference surface of the cam ring 9 (in the radially outward direction), by internal pressure of back pressure chambers 19 each formed in one of the slots 17 on the inner circumference side of the rotor 10, and the centrifugal force according to the rotation of the rotor 10. Moreover, adjacent two of the vanes 18 separate a space between the cam ring 9 and the rotor 10, so as to form a plurality of pump chambers 20.

Moreover, the pressure plate 11 includes a first suction opening 21 which is an arc shape, which is formed by cutting in the circumferential direction on one end surface (a first end surface) 11 a of the pressure plate 11 on the rotor 10's side, in a region (hereinafter, referred to as a suction region) in which volumes of the pump chambers 20 are gradually increased in accordance with the rotation of the rotor 10, as shown in FIG. 1 and FIG. 2. The housing cover 6 includes a second suction opening 22 which is an arc shape, which is formed by cutting in the circumferential direction on one end surface (a first end surface) 6 a of the housing cover 6, in a region (hereinafter, referred to as a suction region) in which volumes of the pump chambers 20 are gradually increased in accordance with the rotation of the rotor 10, as shown in FIG. 1 and FIG. 2.

As shown in FIG. 2, the first suction opening 21 is connected through a suction hole 23 formed in the pressure plate 11, to a first suction pressure chamber 24 formed (opened) on the bottom wall portion 5 b of the housing main body 5. This first suction pressure chamber 24 is connected through a connection passage 26 to a suction opening 25 formed and opened on (toward) the outer circumference portion of the cylindrical portion 5 a.

On the other hand, the second suction opening 22 is connected to a second suction pressure chamber 27 formed and opened on an inner end surface 6 a of the housing cover 6. This second suction pressure chamber 27 is connected through a connection passage 28 to the suction opening 25.

With this, the hydraulic oil which is the hydraulic fluid stored in an oil pan (not shown) is sucked into the pump chambers 20 based on the pump suction function generated in the suction region.

Moreover, as shown in FIG. 1 and FIG. 2, a first discharge opening 29 and a second discharge opening 30 which have arc shapes are formed, by cutting, in the circumferential direction, in a region (hereinafter, referred to as a discharge region) in which the volumes of the pump chambers 20 are gradually decreased in accordance with the rotation of the rotor 10, on the one end surface 11 a of the pressure plate 11 which is on the rotor 10's side and on the inner end surface 6 a of the housing cover 6.

The first discharge opening 29 on the housing main body 5's side is connected to one end portion the discharge passage 33 (cf. FIG. 3 and FIG. 4) through the discharge hole 31 which is formed in the pressure plate 11, and the discharge pressure chamber 32 formed and opened on the bottom wall portion 5 b of the housing main body 5. This discharge passage 33 has the other end portion connected through pipings (not shown) to the CVT, so as to supply the hydraulic fluid discharged from the first discharge opening 29 to the CVT.

Furthermore, as shown in FIG. 3 and FIG. 4, the discharge passage 33 includes a metering orifice 34 which is provided in the middle of the discharge passage 33. The discharge passage 33 generates the pressure difference of the hydraulic fluid by the metering orifice 34.

Besides, the pressure plate 11 includes a first back pressure port 35 which is formed on the one end surface 11 a of the pressure plate 11, which is formed into a substantially annular shape, and which confronts the back pressure chambers 19. The housing cover 6 includes a second back pressure port 36 which is formed on the inner end surface 6 a of the housing cover 6, which is formed into a substantially annular shape, and which confronts the back pressure chambers 19. These back pressure ports 35 and 36 are connected through introduction holes (not shown) to the discharge pressure chamber 32. With this, these back pressure ports 35 and 36 are arranged to introduce (receive) the discharge pressure, and to supply the discharge pressure to the back pressure chambers 19. With this, the vanes 18 are urged toward the inner circumference surface of the cam ring 9.

As shown in FIG. 1, a flow rate control valve 37 is provided at an upper end portion of the housing main body 5. The flow rate control valve 37 is arranged to control a flow rate (a flow amount) of the hydraulic oil discharged by the pump element 3.

As shown in FIG. 1, FIG. 3, and FIG. 4, this flow rate control valve 37 includes a cylindrical control valve receiving hole 38 which is formed in the housing main body 5 to be perpendicular to the drive shaft 4; a cylindrical spool valve 39 which is arranged to be moved within the control valve receiving hole 38 in the axial direction; a solenoid 40 which is provided on a first end side of the control valve receiving hole 38 in the axial direction, and which is arranged to provide, to the spool valve 39, an urging force acting toward a second end side of the control valve receiving hole 38 in the axial direction; a plug 41 which closes the opening of the second end side of the control valve receiving hole 38 in the axial direction; and a valve spring 42 which is disposed between the plug 41 and the spool valve 39, and which is arranged to urge the spool valve 39 in the first end side in the axial direction.

As shown in FIG. 3 and FIG. 4, the spool valve 39 includes a first land portion 43 which is disposed on the first end side in the axial direction; a second land portion 44 which is disposed on the second end side in the axial direction; a third land portion 45 which is disposed between the first and second land portions 43 and 44; and a fourth land portion 46 which is disposed between the third land portion 45 and the second land portion 44.

These first to fourth land portions 43 to 46 have outer circumference surfaces which are slid on the inner circumference surface of the control valve receiving hole 38 with first to fourth clearances C1 to C4 which are different clearances (distances).

That is, the first and second clearances C1 and C2 between the outer circumference surfaces of the first and second land portions 43 and 44, and the inner circumference surface of the control valve receiving hole 38 are set to be smaller than the third and fourth clearances C3 and C4 between the outer circumferences of the third and fourth land portions 45 and 46, and the inner circumference surface of the control valve receiving hole 38.

Moreover, as shown in FIG. 1 to FIG. 4, the spool valve 39 separates an inside space of the control valve receiving hole 38 into first to fifth pressure chambers 47 to 51 by the first to fourth land portions 43 to 46.

The first pressure chamber 47 is provided on the first end side which is the solenoid 40's side relative to the first land portion 43. The first pressure chamber 47 is connected through a first spool control pressure introduction passage 52 to the discharge passage 33 on the upstream side of the metering orifice 34. The pressure (the upstream pressure) on the upstream side of the metering orifice 34 is introduced into the inside of the first pressure chamber 47.

The second pressure chamber 48 is provided on the second end side which is the plug 41's side of the second land portion 44. The second pressure chamber 48 is connected through a second spool control pressure introduction passage 53 to the discharge passage on the downstream side of the metering orifice 34. The pressure (the downstream pressure) on the downstream side of the metering orifice 34 is introduced into the inside of the second pressure chamber 48.

The other end surface (on the right side of FIG. 3) of the second land portion 44 which constitutes the second pressure chamber 48 includes a cylindrical spring holding groove 54 that is formed by cutting, and which receives a part of the valve spring 42. The valve spring 42 includes a first end portion which is elastically abutted on a groove bottom of the spring holding groove 54, and a second end portion which is elastically abutted on the one end surface of the plug 41. With this, the valve spring 41 urges the spool valve 39 in the first end side in the axial direction.

The third pressure chamber 49 provided between the first land portion 43 and the third land portion 45, and the fifth pressure chamber 51 provided between the second land portion 44 and the fourth land portion 46 are connected, respectively, through first and second cam control pressure introduction passages 55 and 56 to the discharge passage 33 on the upstream side of the metering orifice 34. These cam control pressure introduction passages 55 and 56 are provided with damper orifices 55 a and 56 a which are cam passage throttling portions.

As shown in FIGS. 3 and 4, the fourth pressure chamber 50 provided between the third land portion 45 and the fourth land portion 46 is connected through a connection hole 57 to the outside of the pump housing 2. The low pressure is introduced into the inside of the fourth pressure chamber 50.

Moreover, first and second annular grooves 58 and 59 are formed, by cutting, in predetermined axial positions of the control valve receiving hole 38 which are overlapped with the outer circumference surfaces of the third and fourth land portions 45 and 46.

As shown in FIG. 1, the first annular groove 58 is connected to the first fluid pressure chamber 14 through a first fluid pressure chamber connection passage 60 formed in the housing main body 5 and the adapter ring 8. On the other hand, the second annular groove 59 is connected to the second fluid pressure chamber 15 through a second fluid pressure chamber connection passage 61 formed in the housing main body 5 and the adapter ring 8.

The solenoid 40 is controlled to be driven in is accordance with driving status of the vehicle, and so on. The solenoid 40 is arranged to push the one end surface of the spool valve 39 through a rod 40 a that is provided within the first pressure chamber 47 to be extended and contracted, so as to auxiliary control the position of the spool valve 39.

Operations and Effects of this Embodiment

First, when the drive shaft 4 is rotated in accordance with the start of the engine, as shown in FIG. 1, the rotor 10 is rotated in a state where the cam ring 9 is in a maximum eccentric state with respect to the rotor 10. Then, the pump operation is performed within the cam ring 9. The hydraulic oil sucked from the suction openings 21 and 22 are pressurized in accordance with the variations of the volumes within the pump chambers 20. Then, this pressurized hydraulic oil is discharged through the first discharge opening 29 to the discharge passage 33. Most of the hydraulic oil discharged to the discharge passage 33 is supplied through the metering orifice 34 to the CVT (not shown).

At this time, a part of the hydraulic oil is introduced from the upstream side of the metering orifice 34 to the first, third, and fifth pressure chambers 47, 49, and 51. Moreover, a part of the hydraulic oil is supplied from the downstream side of the metering orifice 34 to the second pressure chamber 48. The position control of the flow rate control valve 37 and the control of the pump discharge amount according to the position control of the flow rate control valve 37 are performed based on the pressure difference (hereinafter, referred to as the valve is inside pressure difference) between the fluid pressure of the hydraulic oil within the first pressure chamber 47, and the fluid pressure of the hydraulic oil within the second pressure chamber 48.

Hereinafter, these are illustrated in detail. Before the valve inside pressure difference reaches a predetermined value, that is, when the valve inside pressure difference is small, as shown in FIG. 3, the spool valve 39 of the flow rate control valve 37 holds a state where the spool valve 39 is pressed against the first pressure chamber 47 by the spring force of the valve spring 42.

In this case, in the first flow pressure chamber 14, the connection with the third pressure chamber 49 is shut off. The first fluid pressure chamber 14 is connected to the fourth pressure chamber 50. Accordingly, the low pressure is introduced into the inside of the first fluid pressure chamber 14. On the other hand, the second fluid pressure chamber 15 is connected to the fifth pressure chamber 51. With this, the discharge pressure is introduced into the inside of the second fluid pressure chamber 15. Accordingly, the cam ring 9 is held at the maximum eccentric position by the discharge pressure acted to the second fluid pressure chamber 15 and the spring force of the return spring 16. The pump discharge amount of the variable displacement vane pump 1 is increased to be substantially proportional to the increase of the rotation speed of the rotor 10.

Next, when the rotation speed of the rotor 10 is increased, the pressure difference between the front and is the rear of the metering orifice 34 is increased in accordance with the increase of the pump discharge amount, and the valve inside pressure difference becomes equal to or greater than a predetermined value, the spool valve 39 is stroked (moved) by a predetermined amount in the rightward direction of the drawing in accordance with the valve inside pressure difference, as shown in FIG. 4.

Consequently, in the second fluid pressure chamber 15, the connection with the fifth pressure chamber 51 is shut off. The second fluid pressure chamber 15 is connected to the fourth pressure chamber 50. Accordingly, the inside of the second fluid pressure chamber 15 is opened through the connection hole 57 to the outside. Consequently, the second fluid pressure chamber 15 becomes the low pressure. On the other hand, the first fluid pressure chamber 14 being the low pressure is connected with the third pressure chamber 49, so that the discharge pressure is introduced into the first fluid pressure chamber 14. Accordingly, the cam ring 9 is rolled on the rolling support surface 8 a which is the support surface in a direction in which the eccentric amount is decreased by the discharge pressure acted to the first fluid pressure chamber 14 against the spring force of the return spring 16, that is, toward the second fluid pressure chamber 15.

Then, in this embodiment, the first and second pressure chambers 47 and 48 are not used for the eccentric amount control of the cam ring 9, unlike the conventional art. The first and second pressure chambers 47 and 48 are used only for the position control of the spool valve 39.

That is, the first and second pressure chambers 47 and 48 receive the discharge pressures on the upstream side and the downstream side of the metering orifice 34. With this, the first and second pressure chambers 47 and 48 are arranged to perform the position control of the spool valve 39 by this pressure difference. Accordingly, the first and second pressure chambers 47 and 48 are not used for the eccentric amount control of the cam ring 9. The discharge pressure or the low pressure of the third to fifth pressure chambers 49 to 51 are used for this eccentric amount control.

With this, the discharge of the hydraulic oil discharged from the first and second pressure chambers 47 and 48 are decreased. Accordingly, the variations of the pressures of the first and second pressure chambers 47 and 48 are suppressed except for a case in which it (the pressures of the first and second pressure chambers 47 and 48) is varied in accordance with the pressure difference between the front and the rear (the upstream side and the downstream side) of the metering orifice 34. Accordingly, the position control of the spool valve 39 which is determined based on the pressure difference between the pressures of the first and second pressure chambers 47 and 48 is stabilized.

Consequently, the eccentric amount of the cam ring 9 is controlled by selectively supplying the discharge pressure through the third and fifth pressure chambers 49 and 51 to the first and second fluid pressure chambers 14 and 15 based on the disposition (position) of the spool valve 39. Accordingly, the variation of the eccentric amount of the cam ring 9 is similarly suppressed, so that the eccentric amount of the cam ring 9 is stabilized.

Consequently, the unintended (unexpected) variation of the volumes of the pump chambers which are varied in accordance with the eccentric amount of the cam ring 9 is suppressed. Accordingly, it is possible to stabilize the pump discharge amount.

Moreover, in this embodiment, the discharge pressure is introduced, respectively, into the first and third pressure chambers 47 and 49 formed on the both sides of the first land portion 43 in the axial direction. Accordingly, the pressure difference between the first and third pressure chambers 47 and 49 is relatively small. Similarly, the pressure difference between the second and fifth pressure chambers 48 and 51 which are formed on the both sides of the second land portion 44.

Accordingly, as described above, the first and second clearances C1 and C2 between the outer circumferences of the first and second land portions 43 and 44, and the control valve receiving hole 38 can be set to smaller than the third and fourth clearances C3 and C4 between the outer circumferences of the third and fourth land portions 45 and 46, and the control valve receiving hole 38.

When the first and second clearances C1 and C2 are set to the small values in this way, it is possible to improve the sealability (sealing property) of the first and second pressure chambers 47 and 48, and thereby to further improve the accuracy of the position control of the spool valve 39.

Moreover, the posture of the spool valve 39 with respect to the control valve receiving hole 38 is stabilized. Accordingly, it is possible to avoid the problem that the spool valve 39 is largely inclined with respect to the axial direction, so that the much hydraulic oil is leaked. With this, it is possible to suppress the leakage of the hydraulic oil from the first and second pressure chambers 47 and 48, and to further improve the accuracy of the position control of the spool valve 39.

Moreover, it is possible to suppress the problem that the contamination such as the friction powder included in the hydraulic oil enters the first and second clearances C1 and C2 so as to generate the fixation between the first and second land portions 43 and 44 and the control valve receiving hole 38, by the suppression of the leakage of the hydraulic oil from the first and second pressure chambers 47 and 48.

Besides, the above-described structure is advantageous for the variable displacement vane pump 1 for the CVT in which the much contamination is included in the hydraulic oil like this embodiment.

Moreover, the hydraulic oil for the eccentric amount control of the cam ring 9 is supplied, respectively, from the upstream side of the metering orifice 34 to the third and fifth pressure chambers 49 and 51.

Accordingly, in the eccentric amount control of the cam ring 9, the hydraulic oil on the upstream side of the metering orifice 34 is used. The eccentric amount control of the cam ring 9 does not affect the hydraulic oil on the downstream side of the metering orifice 34. Accordingly, the oil amount of the hydraulic oil which passes through the metering orifice 34 substantially corresponds to the oil amount of the hydraulic oil supplied to the CVT.

Accordingly, it is possible to obtain the desired pump discharge amount by controlling the flow rate (the flow amount) only in consideration of the orifice diameter of the metering orifice 34. Consequently, it is possible to ease the control of the spool valve 39.

Moreover, in the embodiment, the damper orifices 55 a and 56 a are provided, respectively, in the first and second cam control pressure introduction passages 55 and 56. Accordingly, it is possible to reduce the disturbance such as the pulsation of the hydraulic oil introduced into the fluid chambers 14 and 15. With this, it is possible to suppress the vibration of the cam ring 9 based on the disturbance such as the pulsation, and thereby to stabilize the pump discharge amount.

On the other hand, the damper orifice and so on are not provided in the first and second spool control pressure introduction passages 52 and 53. With this, the discharge pressure is directly acted to the first and second pressure chambers 47 and 48. Accordingly, it is possible to improve the response of the control of the spool valve 39.

Furthermore, in this embodiment, the solenoid 40 is provided in the flow rate control valve 37. Accordingly, it is possible to vary the pump discharge amount in detail in accordance with the driving state and so on.

At this time, in a case where the rod 40 a of the solenoid 40 is provided at a portion at which the flow of the hydraulic oil is relatively strong (intense), the contamination flows along the surface of the rod 40 a in accordance with the flow of the hydraulic oil into the inside of the solenoid 40, so that the contamination is adhered to the inside of the solenoid. With this, this may provide the adverse influence on the expansion and contraction of the rod 40 a.

However, in this embodiment, the rod 40 a is disposed within the first pressure chamber 47 in which the flow of the hydraulic oil is relatively gentle. Accordingly, it is possible to decrease the contamination flowing into the inside of the solenoid 40, and thereby to effectively suppress the risk of the adhesion between the solenoid 40 and the rod 40 a.

Second Embodiment

FIG. 5 shows a second embodiment according to the present invention. In the second embodiment, a basic structure is identical to that of the first embodiment. Upstream ends of the first and second cam control pressure introduction passages 55 and 56 are connected, respectively, to the downstream side of the metering orifice 34. With this, the downstream pressure of the metering orifice 34 is introduced, respectively, into the third and fifth pressure chambers 49 and 51.

In this embodiment, the eccentric amount control of the cam ring 9 does not affect the position control of the spool valve 39, like the first embodiment. Accordingly, it is possible to stabilize the pump discharge amount. However, the hydraulic oil passing through the metering orifice 34 is used for the eccentric amount control of the cam ring 9. Consequently, the oil amount of the hydraulic oil supplied to the CVT becomes smaller than the oil amount passing through the metering orifice 34.

However, the oil amount of the hydraulic oil supplied to the first and second fluid pressure chambers 14 and 15 in accordance with the eccentric amount control of the cam ring 9 is quantitative. Accordingly, by previously setting the discharge amount to the large amount, it is possible to easily obtain the desired pump discharge amount.

In this way, the hydraulic oil supplied to the third and fifth pressure chambers 49 and 51 are introduced from the same sides of the upstream side or the downstream side of the metering orifice 34. With this, it is possible to easily obtain the desired pump discharge amount.

Third Embodiment

FIG. 6 shows a third embodiment according to the present invention. The third embodiment has a basic structure identical to that of the first embodiment. The upstream end of the second cam control pressure introduction passage 56 is connected to the downstream side of the metering orifice 34. With this, the upstream pressure of the metering orifice 34 is introduced into the third pressure chamber 49. On the other hand, the downstream pressure of the metering orifice 34 is introduced into the fifth pressure chamber 51.

Accordingly, in this embodiment, the upstream pressure of the metering orifice 34 is introduced, respectively, to the first and third pressure chambers 47 and 49. Consequently, the fluid pressures within the first and third pressure chambers 47 and 49 become substantially identical to each other. The pressure difference between the first and third pressure chambers 47 and 49 becomes small. On the other hand, the downstream pressure of the metering orifice 34 is introduced, respectively, to the second and fifth pressure chambers 48 and 51. Accordingly, the fluid pressures within the second and fifth pressure chambers 48 and 51 become identical to each other, so that the pressure difference between the second and fifth pressure chambers 48 and 51 becomes small.

With this, it is possible to effectively suppress the flow of the hydraulic oil into the first and second clearances C1 and C2 between the first and second land portions 43 and 44, and the control valve receiving hole 38. Accordingly, it is possible to further reliably decrease the risk of the adhesion between the first and second land portions 43 and 44 and the control valve receiving hole 38 by the flow of the contamination.

Besides, in this embodiment, the eccentric amount control of the cam ring 9 does not affect the position control of the spool valve 39, like the first embodiment. Accordingly, it is possible to stabilize the pump discharge amount.

In this embodiment, the first cam control pressure introduction passage 55 may be connected to the fifth pressure chamber 51, and the second cam control pressure introduction passage 56 may be connected to the third pressure chamber 49.

Fourth Embodiment

FIG. 7 shows a fourth embodiment according to the present invention. The fourth embodiment has a basic structure identical to that of the first embodiment. The damper orifices 55 a and 56 a of the first and second cam control pressure introduction passages 55 and 56 are omitted. Moreover, there are provided damper orifices 52 a and 53 a which are provided in the first and second spool control pressure introduction passages 52 and 53, and which are spool passage throttling portions.

Accordingly, in this embodiment, the eccentric amount control of the cam ring 9 does not affect the position control of the spool valve 39. Moreover, the hydraulic oil in a state where the disturbance such as the pulsation is decreased by the damper orifices 52 a and 53 a is introduced into the first and second pressure chambers 47 and 48. Accordingly, the vibration of the spool valve 39 is suppressed. Consequently, it is possible to improve the accuracy of the position control of the spool valve 39.

Moreover, the vibration and so on of the cam ring 9 is indirectly suppressed in accordance with the accuracy of the position control of the spool valve 39. Accordingly, it is possible to further stabilize the pump discharge amount.

Fifth and Sixth Embodiments

FIG. 8 shows a fifth embodiment according to the present invention. The fifth embodiment has a basic structure identical to that of the first embodiment. The damper orifice 55 a of the first cam control pressure introduction passage 55 is omitted. The damper orifice 53 a is provided in the second spool control pressure introduction passage 53.

FIG. 9 shows a sixth embodiment. Contrary to the fifth embodiment, the damper orifice 56 a of the second cam control pressure introduction passage 56 is omitted from the first embodiment. The damper orifice 52 a is provided in the first spool control pressure introduction passage 52.

Accordingly, in these embodiments, the eccentric amount control of the cam ring 9 does not affect the position control of the spool valve 39. Consequently, it is possible to stabilize the pump discharge amount.

Moreover, in these embodiments, on the one side, it is possible to improve the accuracy of the position control of the spool valve and to suppress the vibration of the cam ring 9 by the damping effect, and thereby to further effectively stabilize the pump discharge amount.

Seventh Embodiment

FIG. 10 shows a seventh embodiment according to the present invention. The damper orifices 52 a, 53 a, 55 a, and 56 a are provided in all of the control pressure introduction passages 52, 53, 55 and 56.

Accordingly, in this embodiment, the eccentric amount control of the cam ring 9 does not affect the position control of the spool valve 39. Consequently, it is possible to stabilize the discharge amount of the pump.

Moreover, by the damper orifices 52 a, 53 a, 55 a, and 56 a, the accuracy of the position control of the spool valve 39 is improved, and the vibration of the cam ring 9 is suppressed. Accordingly, it is possible to further effectively stabilize the pump discharge amount.

Eighth Embodiment

FIG. 11 shows an eighth embodiment according to the present invention. In this eighth embodiment, the present invention is applied to a variable displacement vane pump 1 of a low pressure type.

This is explained in detail below. In the above-described variable displacement vane pump according to the embodiments, the low pressure or the discharge pressure is selectively introduced, respectively, into the first and second fluid pressure chambers 14 and 15 in accordance with the position of the spool valve 39. However, in this embodiment, the low pressure or the discharge pressure is selectively introduced only into the first fluid pressure chamber 14. The low pressure is always introduced into the second fluid pressure chamber 15 through a communication passage (not shown) which is connected to the suction side.

Accordingly, as shown in FIG. 11, the flow rate control valve 37 does not need to be connected to the second fluid pressure chamber 15. Consequently, the fourth land portion 44 and the fifth pressure chamber 51 are omitted. The fourth pressure chamber 50 and the second pressure chamber 48 are formed on the second end side of the third land portion 45 of the control valve receiving hole 38. Accordingly, the second cam control pressure introduction passage 56 arranged to introduce the discharge pressure to the fifth pressure chamber 51, the second annular groove 59 and the second fluid pressure chamber communication passage 61 which are arranged to introduce the discharge pressure from the fifth pressure chamber 51 to the second fluid pressure chamber 15 are omitted.

Accordingly, in this embodiment, the position control of the cam ring 9 is performed only in accordance with the pressure variation of the first fluid pressure chamber 14. The pump discharge amount is varied based on this.

In this embodiment, the first and second pressure chambers 47 and 48 are used only for the position control of the spool valve 39, like the first embodiment. Accordingly, it is possible to suppress the leakage of the hydraulic oil from the first and second pressure chambers 47 and 48. With this, it is possible to improve the accuracy of the position control of the spool valve 39, and to stabilize the pump discharge amount.

Moreover, in this embodiment, as described above, the low pressure is always introduced into the second fluid pressure chamber 15. The discharge pressure is not acted to the second fluid pressure chamber 15. Accordingly, the problem that the discharge pressure is leaked through the second fluid pressure chamber 15 to the outside is not generated. Consequently, it is possible to suppress the decrease of the pump efficiency.

Besides, in this embodiment, the urging force when the cam ring 9 is moved in the direction in which the eccentric amount with respect to the rotor 10 becomes large, that is, toward the first fluid pressure chamber 14 is small. Accordingly, in a case where the contamination enters and adheres between the cam ring 9 and the pump housing 2 (the pressure plate 11), this adhesion may not be dissolved. Accordingly, this embodiment is preferable to use in a condition in which the contamination within the hydraulic oil is less. For example, this embodiment is advantageous in the pump apparatus for the power steering apparatus.

Ninth Embodiment

FIG. 12 shows a ninth embodiment. In this embodiment, the pump apparatus according to the present invention is applied to the fixed displacement vane pump 71. Besides, in the below explanations, portions identical to those of the above-described embodiments have the same symbols. The repetitive explanations are omitted.

The fixed displacement vane pump 71 includes a pump housing 2; an annular cam ring 72 which is mounted and fixed in the circumferential wall of the pump element receiving chamber 2 a of the pump housing 2; and the rotor 10 which is provided radially inside the cam ring 72, which is rotatably driven by the drive shaft 4; and which includes an outer circumference portion in which a plurality of the slots 17 are formed.

The cam ring 72 includes an elliptic inside space to which are formed radially inside the cam ring 72. The inside space of the cam ring 72 are partitioned by the plurality of the vanes 18 which are moved within the slots 17 in the radially outward direction and in the radially inward direction, so as to form the plurality of the pump is chambers 20.

Furthermore, the suction passage 73 is connected to the suction region in which the volumes of the pump chambers 20 are generally enlarged in accordance with the rotation of the rotor 10, so as to suck the hydraulic oil from the oil pan 74. On the other hand, the discharge passage 33 is connected to the discharge region in which the volumes of the pump chambers 20 is gradually decreased in accordance with the rotation of the rotor 10, so as to supply the hydraulic oil through the discharge passage 33 to the CVT (not shown).

Then, the discharge passage 33 is provided with the metering orifice 34 which is arranged to generate the pressure difference to the hydraulic oil flowing within the discharge passage 33; and a flow rate (flow amount) control valve 37 which is arranged to control the flow rate of the hydraulic oil supplied to the CVT based on the pressure difference between the front and the rear (the upstream and downstream sides) of the metering orifice 34.

The flow rate control valve 37 includes a cylindrical control valve receiving hole 38; a cylindrical spool valve 39 which is arranged to be moved within the control valve receiving hole 38 in the axial direction; and a valve spring 42 which is arranged to urge the spool valve 39 toward the first end side of the axial direction.

The spool valve 39 includes three first to third land portions 43 to 45 which are positioned at predetermined axial positions. The land portions 43 to 45 separate the inside space of the control valve receiving hole 38 into the first to fourth pressure chambers 47 to 50.

The upstream pressure of the metering orifice 34 is introduced through the first spool control pressure introduction passage 52 to the first pressure chamber 47. On the other hand, the downstream pressure of the metering orifice 34 is introduced through the second spool control pressure introduction passage 53 to the second pressure chamber 48. The position control of the spool valve 39 is performed based on the pressure difference of these. Besides, the damper orifices 52 a and 53 a are formed, respectively, in the spool control pressure introduction passages 52 and 53.

The upstream pressure of the metering orifice 34 which is bifurcated from the first spool control pressure introduction passage 52 is introduced into the third pressure chamber 49. Moreover, the third pressure chamber 49 is arranged to be connected to the connection hole 57 connected to the outside of the pump housing 2, in accordance with the movement of the spool valve 39.

Accordingly, in this embodiment, before the valve inside pressure difference between the first pressure chamber 47 and the second pressure chamber 48 reaches the predetermined value, that is, while the engine speed is relatively small, the state in which the spool valve 39 is pressed on the left side of FIG. 12 by the valve spring 42 is held. In this case, the third pressure chamber 49 and the communication hole 57 are shut off by the third land portion 45. Accordingly, the hydraulic oil is not discharged from the communication hole 57. The pump discharge amount of the fixed displacement vane pump 71 is increased to be substantially proportional to the increase of the rotation speed of the rotor 10.

On the other hand, when the rotation speed of the rotor 10 is increased, the pressure difference between the front and the rear (the upstream side and the downstream side) of the metering orifice 34 is increased in accordance with the increase of the pump discharge amount, and the valve inside pressure difference becomes equal to or greater than the predetermined value accordingly, the spool valve 39 is moved toward the right side of FIG. 12. Then, the third pressure chamber 49 and the communication hole 57 are connected with each other. A part of the hydraulic oil flowing in the discharge passage 33 is discharged from the communication hole 57 to the outside of the pump housing 2. Accordingly, the pump discharge amount is decreased.

Accordingly, in this embodiment, when the pump apparatus is the fixed displacement pump, it is possible to variably control the pump discharge amount with respect to the CVT by using the flow rate control valve 37.

Then, in this embodiment, the hydraulic oil is not discharged from the first and second pressure chambers 47 and 48. The first and second pressure chambers 47 and 48 are used only for the position control of the spool valve 39.

With this, it is possible to suppress the leakage of the hydraulic oil from the first and second pressure chambers 47 and 48. Accordingly, the variation of the fluid pressures of the first and second pressure chambers 47 and 48 are suppressed. Consequently, the position control of the spool valve 39 which is determined based on the pressure difference of these is stabilized.

Therefore, it is possible to suppress and stabilize the variation of the oil amount of the hydraulic oil discharged from the third pressure chamber 49 to the outside of the pump housing 2.

Accordingly, in this embodiment, it is possible to improve the accuracy of the position control of the spool valve 39, and thereby to stabilize the pump discharge amount.

Besides, in this embodiment, the solenoid 40 may be provided on the one end side of the spool valve 39 although this is not shown in the drawing. With this, it is possible to vary the pump discharge amount in detail in accordance with the driving condition and so on. In this case, the disposition of the rod 40 a is positioned in the inside of the first pressure chamber 47 in which the flow of the hydraulic oil is relatively small, like the first embodiment. Accordingly, it is possible to suppress the risk of the adhesion of the contamination.

The entire contents of Japanese Patent Application No. 2014-256750 filed Dec. 19, 2014 are incorporated herein by reference.

Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims. 

What is claimed is:
 1. A pump apparatus comprising: a pump housing including a pump element receiving portion which is formed within the pump housing; a drive shaft which is inserted within the pump element receiving portion, and which is rotatably supported by the pump housing; a rotor which is provided within the pump element receiving portion, which is driven by the drive shaft to rotate, and which includes a plurality of slots in a circumferential direction; a plurality of vanes which are provided in the slots of the rotor to be moved in a radially outward direction and in a radially inward direction; a cam ring which is arranged to be moved within the pump element receiving portion, which has an annular shape, and which forms a plurality of pump chambers radially inside the cam ring, with the rotor and the vanes; a suction opening which is formed in the pump housing, and which is opened in a suction region in which volumes of the plurality of the pump chambers are increased in accordance with the rotation of the rotor; a discharge opening which is formed in the pump housing, and which is opened in a discharge region in which the volumes of the pump chambers are decreased in accordance with the rotation of the rotor; a discharge passage connected with the discharge opening; a metering orifice which is formed in the middle of the discharge passage; a first fluid pressure chamber which is formed between the pump element receiving portion and the cam ring, and which is formed on a side on which a volume of the first fluid pressure chamber is decreased when the cam ring is moved on the side on which the eccentric amount of the cam ring with respect to the drive shaft is increased; a second fluid pressure chamber which is formed between the pump element receiving portion and the cam ring, and which is formed on a side on which a volume of the second fluid pressure chamber is decreased when the cam ring is moved on the side on which the eccentric amount of the cam ring with respect to the drive shaft is increased; a control valve receiving hole which is formed in the pump housing; a spool valve which is arranged to be moved within the control valve receiving hole, the spool valve including; a first land portion which is provided on a first end side of the spool valve in a movement direction of the spool valve, a second land portion which is provided on second end side of the spool valve in the movement direction of the spool valve, and a third land portion which is provided between the first land portion and the second land portion in the movement direction of the spool valve; a first pressure chamber which is formed within the control valve receiving hole, which is provided on the first end side of the first land portion in the movement direction of the spool valve, and into which an upstream pressure of the metering orifice is introduced; a second pressure chamber which is formed within the control valve receiving hole, which is formed on second end side of the second land portion in the movement direction of the spool valve, and into which a downstream pressure of the metering orifice is introduced; a third pressure chamber which is formed within the control valve receiving hole, which is provided between the first land portion and the third land portion in the movement direction of the spool valve, and into which the pressure of the discharge passage is introduced; a fourth pressure chamber which is formed within the control valve receiving hole, which is provided between the second land portion and the third land portion in the movement direction of the spool valve, and into which a low pressure is introduced; and a first fluid pressure chamber side communication passage which is formed in the pump housing, which includes a first end portion which is connected to the valve receiving hole, and a second end portion which is connected to the first fluid pressure chamber, and which is arranged to selectively supply the pressure of the third pressure chamber and the pressure of the fourth pressure chamber to the first fluid pressure chamber in accordance with the movement of the spool valve.
 2. The pump apparatus as claimed in claim 1, wherein the pump apparatus further comprises a fourth land portion which is provided between the second land portion and the third land portion in the movement direction of the spool valve, a fifth pressure chamber which is formed within the control valve receiving hole, which is formed between the second land portion and the fourth land portion in the movement direction of the spool valve, and into which the pressure of the discharge passage is introduced, and a second fluid pressure chamber side communication passage which is formed in the pump housing, which includes a first end portion connected to the valve receiving hole, and a second end portion connected to the second fluid pressure chamber, and which is arranged to selectively supply the pressure of the fifth pressure chamber and the pressure of the fourth pressure chamber to the second fluid pressure chamber in accordance with the movement of the spool valve; and the fourth pressure chamber is formed between the third land portion and the fourth land portion in the movement direction of the spool valve.
 3. The pump apparatus as claimed in claim 1, wherein the spool valve is formed so that clearances between an outer circumference surface of the first land portion and an outer circumference surface of the second land portion, and an inner circumference surface of the control valve receiving hole are smaller than clearances between an outer circumference surface of the third land portion and an outer circumference surface of the fourth land portion, and the inner circumference surface of the control valve receiving hole.
 4. The pump apparatus as claimed in claim 3, wherein the pump apparatus is connected through the discharge passage to a continuously variable transmission to supply the hydraulic fluid to the continuously variable transmission.
 5. The pump apparatus as claimed in claim 2, wherein the third pressure chamber and the fifth pressure chamber receive the pressure of the discharge passage on the same side of the upstream side or the downstream side of the metering orifice.
 6. The pump apparatus as claimed in claim 5, wherein the third pressure chamber and the fifth pressure chamber receive the pressure of the discharge passage on the upstream side of the metering orifice.
 7. The pump apparatus as claimed in claim 5, wherein the third pressure chamber and the fifth pressure chamber receive the pressure of the discharge passage on the downstream side of the metering orifice.
 8. The pump apparatus as claimed in claim 2, wherein the third pressure chamber receives the pressure of the discharge passage on an upstream side of the metering orifice; and the fifth pressure chamber receives the pressure of the discharge passage on a downstream side of the metering orifice.
 9. The pump apparatus as claimed in claim 3, wherein the pump apparatus further comprises a first cam passage throttling portion which is provided in a first cam control pressure introduction passage connecting the third pressure chamber and the discharge passage, and a second cam passage throttling portion provided in a second cam control pressure introduction passage connecting the fifth pressure chamber and the discharge passage.
 10. The pump apparatus as claimed in claim 2, wherein the pump apparatus further comprises a first spool passage throttling portion which is provided in a first spool control pressure introduction passage connecting the first pressure chamber and the discharge passage on an upstream side of the metering orifice, and a second spool passage throttling portion which is provided in a second spool control pressure introduction passage connecting the second pressure chamber and the discharge passage on a downstream side of the metering orifice.
 11. The pump apparatus as claimed in claim 2, wherein the pump apparatus further includes a first spool control pressure introduction passage connecting the first pressure chamber and the discharge passage on an upstream side of the metering orifice, a first cam control pressure introduction passage connecting the third pressure chamber and the discharge passage, a second cam control pressure introduction passage connecting the fifth pressure chamber and the discharge passage, and a second spool control pressure introduction passage connecting the second pressure chamber and the discharge passage on a downstream side of the metering orifice; and the first spool control pressure introduction passage and the first cam control pressure introduction passage, or the second cam control pressure introduction passage and the second spool control pressure introduction passage have throttling portions.
 12. The pump apparatus as claimed in claim 2, wherein the pump apparatus further includes a first spool control pressure introduction passage connecting the first pressure chamber and the discharge passage on an upstream side of the metering orifice, a first cam control pressure introduction passage connecting the third pressure chamber and the discharge passage, a second cam control pressure introduction passage connecting the fifth pressure chamber and the discharge passage, and a second spool control pressure introduction passage connecting the second pressure chamber and the discharge passage on a downstream side of the metering orifice; and each of the first spool control pressure introduction passage, the first cam control pressure introduction passage, the second cam control pressure introduction passage, and the second spool control pressure introduction passage has a throttling portion.
 13. The pump apparatus as claimed in claim 1, wherein the second fluid pressure chamber receives a suction pressure.
 14. The pump apparatus as claimed in claim 1, wherein the pump apparatus further comprises a solenoid which is controlled to be driven in accordance with a driving state of a vehicle, and which is arranged to push the first end side of the spool valve through a rod provided to extend within the first pressure chamber, and thereby to perform a position control of the spool valve.
 15. A pump apparatus comprising: a pump housing including a pump element receiving portion which is formed within the pump housing; a drive shaft which is inserted within the pump element receiving portion, and which is rotatably supported by the pump housing; a rotor which is provided within the pump element receiving portion, which is driven by the drive shaft to rotate, and which includes a plurality of slots in a circumferential direction; a plurality of vanes which are provided in the slots of the rotor to be moved in a radially outward direction and in a radially inward direction; a cam ring which is provided within the pump element receiving portion, which has an annular shape, and which forms a plurality of pump chambers radially inside the cam ring, with the rotor and the vanes; a suction opening which is formed in the pump housing, and which is opened in a suction region in which volumes of the plurality of the pump chambers are increased in accordance with the rotation of the rotor; a discharge opening which is formed in the pump housing, and which is opened in a discharge region in which the volumes of the pump chambers are decreased in accordance with the rotation of the rotor; a discharge passage connected with the discharge opening; a metering orifice which is formed in the middle of the discharge passage; a control valve receiving hole which is formed in the pump housing; a spool valve which is arranged to be moved within the control valve receiving hole, the spool valve including; a first land portion which is provided on a first end side of the spool valve in a movement direction of the spool valve, a second land portion which is provided on second end side of the spool valve in the movement direction of the spool valve, and a third land portion which is provided between the first land portion and the second land portion in the movement direction of the spool valve; a first pressure chamber which is formed within the control valve receiving hole, which is provided on the first end side of the first land portion in the movement direction of the spool valve, and into which an upstream pressure of the metering orifice is introduced; a second pressure chamber which is formed within the control valve receiving hole, which is formed on second end side of the second land portion in the movement direction of the spool valve, and into which a downstream pressure of the metering orifice is introduced; a third pressure chamber which is formed within the control valve receiving hole, which is provided between the first land portion and the third land portion in the movement direction of the spool valve, and into which the pressure of the discharge passage is introduced; a fourth pressure chamber which is formed within the control valve receiving hole, which is provided between the second land portion and the third land portion in the movement direction of the spool valve, and into which a low pressure is introduced; and an outlet passage which is provided in the pump housing, which includes a first end portion connected to the valve receiving hole, and a second end portion connected to the suction opening, and which is arranged to discharge the hydraulic fluid within the third pressure chamber to the suction opening's side in accordance with the movement of the spool valve.
 16. The pump apparatus as claimed in claim 15, wherein the pump apparatus further comprises a solenoid which is controlled to be driven in accordance with a driving state of a vehicle, and which is arranged to push the first end side of the spool valve through a rod provided to extend within the first pressure chamber, and thereby to perform a position control of the spool valve. 